U.S. Pat. No. 5,165,651 discloses a method of fabrication of a hollow form made of an aggregate filled thermosetting resin, the disclosure of which is incorporated herein by reference. In this application, a two-piece male-female mold is constructed of plywood. Pressboard was also used to fabricate the two-piece male-female mold. In each instance only one hollow form was made from each two-piece male-female mold. To remove the hollow form fabricated in the plywood or pressboard mold required that the plywood or pressboard be torn free of the form.
The present invention overcomes the disadvantages of the plywood or pressboard molds in a number of ways. First, the high cost in labor and materials in fabricating multiple molds is eliminated, each plywood or pressboard mold taking two to six man days of labor to fabricate and essentially no recovery of material. Second, a standardization of the hollow forms results from a reuseable mold, the size of the upper surface of the form can be easily duplicated. There are other advantages in the use of thermoplastic sheets, especially polyethylene sheets, in that the aggregate filled thermosetting resins used in fabricating the form do not stick to the thermoplastic once the thermosetting resin cures and cools. Further, the thermoplastic sheets are easily cleaned for reuse and the strength of the sheets are such that the same mold may be used over and over again.